Societal energy demands are constantly increasing while fossil fuel resources, the main energy resource of many national energy systems, are limited and predicted to become scarcer, and as a result to become more expensive in coming years. Furthermore, many concerns exist regarding the environmental impacts associated with continuous drilling and pumping of the fossil fuels from the Earth's crust and increasing energy consumption. Specifically, concerns have been raised regarding the possible effect of increased use of fossil fuels on climate change and atmospheric pollution.
Changes are required in energy systems, partly through the adoption of advanced energy technologies and systems to address these serious environmental concerns. The anticipated worldwide increase in energy demand and concern regarding environmental problems has become a driving force for the utilization of more efficient and cleaner energy technologies. Examples include advanced systems for waste energy recovery and energy integration. Important technologies that can contribute to avoiding environmental problems and increasing the efficiency of energy consumption include thermal energy storage (TES), and more specifically, thermochemical energy storage (TCES).
Thermal energy storage is especially an important technology in systems involving renewable energy sources as well as other energy resources as it can make their operation more efficient. One example is bridging the periods between when energy is harvested and when it is needed. For example, the next generation of advanced concentrating solar power (CSP) plants are being designed to increase the sunlight to electricity conversion efficiency, and one of the major techniques to enact this increase is through the use of receivers, heat transfer fluids (HTF), thermal energy storage systems, and power blocks that operate at high temperatures. It was found that CSP systems, for example, require thermal energy storage to be competitive with conventional grid scale power generation systems. Thus, TES can play an important role in increasing the contribution of various types of renewable energy in the energy production of regions and countries.
Various TES technologies and applications exist. The selection of a TES system for a particular application depends on many factors, including storage duration, economics, supply and utilization temperature requirements, storage capacity, heat loss and available space.
More compact TES can be achieved based on a system that utilize chemical reactions. However, the current-state-of the-art molten salt based thermal storage systems are unable to operate in the high temperature range required, for example, in CSP systems. High temperature thermal energy is generally stored as sensible heat in either molten salt or synthetic organic heat transfer oil. However, these mediums store heat in a very low volumetric energy density and are not able to store heat above 500° C.
Therefore, thermochemical energy storage systems exhibiting very high volumetric energy density and capable of operating through a wide temperature range are needed. Even further, improved methods for storing energy would be desirable.
Accordingly, such thermochemical energy storage systems and methods for storing energy are described herein.